The present invention relates to a heater apparatus for heating fluid medium confined in a hermetically sealed chamber and more particularly to an apparatus which includes a heating element that extends directly into the sealed chamber.
In the refrigerant compressor art, it is generally known to heat the fluid medium confined in a crankcase of a refrigerant compressor by means of a PTC thermistor device confined in a heat conductive ceramic case such as disclosed in U.S. Pat. No. 4,236,065, issued to M. A. Yashin et al. on Nov. 25, 1980 and U.S. Pat. No. 4,644,316 issued to M. Takeuchi et al. on Feb. 17, 1987. An appropriately sized, heat conductive metallic sleeve member which is closed at one end and open at the other, has its opened end sealed to the wall of the crankcase with its closed end projecting into the crankcase chamber. A ceramic encased PTC heater is inserted into the sleeve opening and connected to an electrical source to heat fluid medium in the crankcase chamber through the surrounding heat conductive metallic sleeve member projecting into the crankcase.
The present invention recognizing that such past apparatus presents problems in heat loss through the encasing heat conductive metallic sleeve and the housing to which it is attached and that the wattage required to apply the required heat is not directly responsive to the fluid medium confined by the crankcase housing and surrounding ambient conditions, provides a novel crankcase heater arrangement which avoids these past difficulties by eliminating the comparatively costly and difficult to manufacture and assemble heat conductive sleeve and by inserting a heating member electrically connected to a conventionally mounted terminal assembly to heat the fluid medium in a more direct manner without the aforedescribed concomitant heating losses through a heat conductive sleeve and the crankcase housing to which it is mounted. Further, the crankcase heater arrangement of the present invention is more directly responsive to confined fluid medium and ambient temperature conditions so as to minimize wattage consumption and thus optimize overall heating efficiency. In addition, the present invention facilitates the ready and selective positioning of the heater unit to minimize past problems of fluid medium slugging and air entrapment between heater and housing.
Various other features of the present invention will become obvious to one skilled in the art upon reading the disclosure set forth herein.